1. Field of the Invention
The present invention relates to an LED lighting apparatus equipped with a high-efficiency power supply. In more particular, the present invention relates to an LED lighting apparatus equipped with a high-efficiency power supply, capable of representing high power efficiency even in a low-power LED lighting apparatus by recycling a surplus voltage to charge a condenser, which supplies power to the controller, with the surplus voltage if the surplus voltage is generated from an LED acting as a load after a rectified voltage supplied to the LED has been consumed in the LED according to a design value.
2. Description of the Related Art
An LED (light emitting diode) is an electrical/optical conversion semiconductor device to emit a light as electricity is applied thereto, and extensively used for a backlight of a display. In addition, since the electrical/optical conversion efficiency of the LED is more increased with the advance of technologies as compared with existing light bulbs and existing fluorescent lamps, the LED has been extensively used as general lighting devices. However, in the LED, since a current greatly varies even if a voltage slightly varies, the current must be accurately controlled.
As shown in FIG. 1, an LED lighting apparatus according to the related art includes an AC voltage source 910 to supply an AC voltage, a rectifier 940 to convert the AC voltage received from the AC voltage source 910 into a DC rectified voltage Vrect, first to third LED blocks 971 to 973 that act as loads and are driven by the rectified voltage, which is an output of the rectifier 940, a switch block including first to third by-pass switches SW11 to SW13 arranged in series to by-pass the currents of the LED blocks, a current source CS9 to restrict the current of the load, a controller 904 to control the switch block and a current source, a power supplying condenser C9 to supply a DC power to the controller 904, and a resistor R9, a diode D9, and a zener diode ZD9 for overvoltage protection that constitute a charging circuit to charge the power supplying condenser C9.
Accordingly, if the AC voltage source 910 starts to supply a commercial voltage, the power supplying condenser C9, which supplies a DC power to the controller, is charged with the voltage by the charging circuit, and the controller 904 controls the switch block so that LED blocks suitable for the instantaneous rectified voltage Vrect are arranged in series, and restricts an amount of a current flowing through the loads by controlling the current source.
Hereinafter, the charging circuit will be described in more detail. If the rectifier 940 starts to supply the rectified voltage Vrect, a current, which has passed through the resistor R9 and the diode D9 connected to each other in series, starts to be charged in the condenser C9 for supply DC power. Then, if the condenser C9 is charged with the current, so that a voltage Vcc across both terminals of the condenser C9 exceeds the minimum voltage (for example, DC 5V) to operate the controller 904, the controller 904 commences the operation thereof.
Meanwhile, if the DC power supplying condenser C9 is excessively charged, so that the voltage Vcc across both terminals of the DC power supplying condenser C9 reaches the maximum operating voltage (for example, DC 28V) to operate the controller 904, the zener diode ZD9 for overvoltage protection is operated to prevent the voltage of the condenser C9 from being charged up. In addition, if the rectified voltage Vrect is dropped to the voltage Vcc across both terminals of the DC power supplying condenser C9 or less, the diode D9 prevents the DC power supplying condenser C9 from being discharged through the resistor R9.
Hereinafter, the problems caused in the related art will be described.
First, the AC voltage source 910 supplies a commercial voltage of 220 Vrms. On the assumption that the maximum operating voltage of the controller 904 is DC 28V (i.e., 20 Vrms), and the current required for the controller 904 is 1 mA, the power consumed in the resistor R9 becomes 200 mW obtained by 200 Vrms×1 mA.
Accordingly, when high power is required, for example, when a 20 watt LED lamp is driven, about 1% of power is used to generate the driving power of the controller 904. In addition, when low power is required, for example, when a 4.4 watt LED lamp (220V×20 mA) is driven, about 4.5% of power is used to generate the driving power of the controller, so that power efficiency is lowered. Accordingly, the improvement is required to increase power efficiency in the low-power LED lighting apparatus.